[FIXED JENKINS-19017] - FileParameter - Handle non-null file parameters as different values

The change prevents the issue when Jenkins merges builds with different files coming from one source (It may happen!).

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
[JENKINS-19017] - Unit tests

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Merge pull request #1411 from synopsys-arc-oss/JENKINS-19017

[FIXED JENKINS-19017] - FileParameter - Handle non-null file parameters as different values